Excel Optimization for App Data Processing

I have an Excel file that pulls data from an app, processes it through some formulas, and sends it back via API or Excel commands. All functions are operational but there's a slight delay. I need an expert to enhance the efficiency of the sheet to eliminate this lag.

Key Requirements:
- Optimize data processing speed
- Improve data lookup efficiency
- Enhance data transmission speed

Skills and Expertise Needed:
- Proficient in Excel
- Experienced in VBA programming
- Knowledgeable in data processing and transmission optimization techniques